Learning While Sleeping Like a Baby (WSJ-sub req):
Children may sleep so much because they have so much to learn (though toddlers may find that scant consolation for the dreaded bedtime). It's paradoxical to try to get children to learn by making them wake up early to get to school and then stay up late to finish their homework.
Of the many benefits of homeschooling, two of the most obvious are not having to wake kids up in the morning to get them ready for school, thus allowing them to get the sleep they need, and not having to worry about the kids staying up late at night to complete homework. You might even say it's a more natural way of learning.